Three-dimensional geometry measurement apparatus and three-dimensional geometry measurement method

ABSTRACT

A three-dimensional geometry measurement apparatus includes: a projection part that projects a projection image onto an object to be measured; an image capturing part that generates a captured image by capturing the object to be measured on which the projection image is projected; a relationship identification part that identifies a projection pixel position having correspondence with a captured pixel position; and a defective pixel determination part that determines whether the pixel at the captured pixel position is a defective pixel on the basis of a positional relationship between a projection light beam starting from the projection part and passing through the pixel at the projection pixel position and a captured light beam starting from the image capturing part and passing through the pixel at the captured pixel position having correspondence.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to Japanese Patent Applicationsnumber 2018-172951, filed on Sep. 14, 2018. The contents of thisapplication are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a three-dimensional geometrymeasurement apparatus and a three-dimensional geometry measurementmethod for measuring a three-dimensional geometry of an object to bemeasured.

Methods for measuring an object to be measured without making anycontact can be divided into two: a passive technique such as a stereomethod; and an active technique such as a triangulation method, atime-of-flight method, and a confocal method. Among them, use of thetriangulation method is increasing in various fields such as productquality management and reverse-engineering

A light-pattern projecting method uses the principle of thetriangulation method and performs a three-dimensional (3D) geometrymeasurement by projecting a pattern of stripes from a projector onto theobject to be measured and then by capturing the pattern that changesalong the geometry of the object to be measured with a camera. JapaneseUnexamined Patent Application Publication No. 2009-094295 discloses ameasurement apparatus for measuring a height of an electronic componentbased on a captured image obtained by imaging an optical cutting linewhen line light is projected onto the electronic component.

Because the light-pattern projecting method is capable of measuring alarger area at one time when projecting an image including a pluralityof patterns of stripes on to the object to be measured, it enables afaster measurement of the 3D geometry.

In light-pattern projecting method, when a surface of the object to bemeasured is glossy, multiple reflections occur, that is, the projectedlight from the projector repeatedly reflects from a surface of theobject to be measured. Due to the multiple reflections, there was aproblem that measurement accuracy is reduced.

As methods to prevent the multiple reflections, a method of applying ananti-multiple-reflection spray over the surface of the object to bemeasured, a mask which cuts a part of the projected light from theprojector in its light path, and the like have been employed. However,in the method of applying the anti-multi-reflection spray over thesurface of the object to be measured, there was a problem that thenumber of man-hours for rinsing increased. There was another problemthat the anti-multi-reflection spray cannot be applied in an environmentwhere a high degree of cleanness needs to be maintained.

Also, the method of using the mask is associated with a problem that themeasurement time is increased since the number of times that the patternis projected onto the object to be measured needed to be increased tocut a part of the projected light from the projector. Further, in thismethod, there was another problem that different masks need to becreated for each individual object to be measured. In addition to themultiple reflections, for example, there was another problem that themeasuring accuracy is lowered due to blurring of an imaging system atedges of the object to be measured or at places where luminance changeis large.

BRIEF SUMMARY OF THE INVENTION

This invention focuses on these points, and an object of the inventionis to provide a three-dimensional geometry measurement apparatus and athree-dimensional geometry measurement method, which are capable ofpreventing a reduction of measurement accuracy caused by multiplereflections, blurring of the imaging system, or the like.

A three-dimensional geometry measurement apparatus according to thefirst aspect of the present invention is a three-dimensional geometrymeasurement apparatus that measures a three-dimensional geometry of anobject to be measured by projecting, onto the object to be measured, aprojection image including a light pattern in which luminance changesdepending on a position, and includes: a projection part that projectsthe projection image onto the object to be measured; an image capturingpart that generates a captured image capturing the object to be measuredon which the projection image is projected; a relationshipidentification part that identifies a projection pixel position which isa position of a pixel of the projection image having correspondence witha captured pixel position which is a position of a pixel of the capturedimage; and a defective pixel determination part that determines whetheror not the pixel at the captured pixel position is a defective pixel onthe basis of a positional relationship between (i) a projection lightbeam starting from the projection part and passing through the pixel atthe projection pixel position and (ii) a captured light beam startingfrom the image capturing part and passing through the pixel at thecaptured pixel position having correspondence with the projection pixelposition.

A three-dimensional geometry measurement method according to the secondaspect of the present invention is a three-dimensional geometrymeasurement method that measures a three-dimensional geometry of anobject to be measured by projecting, onto the object to be measured, aprojection image including a light pattern in which luminance changesdepending on a position in a predetermined direction, the methodincludes steps of: projecting the projection image onto the object to bemeasured by a projection part; generating, by an image capturing part, acaptured image by capturing the object to be measured on which theprojection image is projected; identifying a projection pixel positionwhich is a position of a pixel of the projection image havingcorrespondence with a captured pixel position which is a position of apixel of the captured image; and determining whether or not the pixel atthe captured pixel position is a defective pixel on the basis of apositional relationship between (i) a projection light beam startingfrom the projection part and passing through the pixel at the projectionpixel position and (ii) a captured light beam starting from the imagecapturing part and passing through the pixel at the captured pixelposition having correspondence with the projection pixel position.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1C illustrate an outline of a 3D geometry measurementapparatus according to the first embodiment.

FIGS. 2A and 2B each show a projection image which a projection partprojects onto an object to be measured.

FIG. 3 shows a configuration of the 3D geometry measurement apparatus.

FIGS. 4A to 4F respectively show examples of types of projection imageswhich a projection control part projects.

FIGS. 5A to 5D respectively show examples of gradation light patternshaving sinusoidal luminance distributions.

FIG. 6 shows examples of Gray codes corresponding to binary lightpatterns shown in FIGS. 4C to 4F.

FIGS. 7A and 7B each illustrate multiple reflections.

FIG. 8 shows a light path of direct reflection light.

FIG. 9 shows a light path of multiply reflected light.

FIG. 10 illustrates a method of determining a defective pixel by adefective pixel determination part:

FIG. 11 illustrates another method of determining the defective pixel bythe defective pixel determination part.

FIG. 12 illustrates still another method of determining the defectivepixel by the defective pixel determination part.

FIG. 13 is a flowchart for illustrating a procedure of a defective pixeldetermination process performed by the defective pixel determinationpart.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the present invention will be described through exemplaryembodiments of the present invention, but the following exemplaryembodiments do not limit the invention according to the claims, and notall of the combinations of features described in the exemplaryembodiments are necessarily essential to the solution means of theinvention.

First Embodiment [Outline of a 3D Geometry Measurement Apparatus 100]

FIGS. 1A to 1C illustrate the outline of a 3D geometry measurementapparatus 100 according to the first embodiment. FIG. 1A shows aconfiguration of the 3D geometry measurement apparatus 100. The 3Dgeometry measurement apparatus 100 measures a 3D geometry of the objectto be measured by projecting, onto the object to be measured, aprojection image including light patterns in which luminance changesdepending on a position in a predetermined direction. The light patternsare, for example, stripe patterns. Details of the light patterns will bedescribed below. The 3D geometry measurement apparatus 100 includes aprojection part 1, an image capturing part 2, and a control part 3.

The projection part 1 is a projection apparatus having a light sourcesuch as a light emitting diode or a laser, a projection lens, and aliquid crystal, a micro mirror, or the like. The projection part 1projects a plurality of respectively different projection imagesincluding light patterns onto a measurement surface of the object to bemeasured.

The image capturing part 2 is a capturing apparatus that has a lens 21and an imaging element 22, an optical filter (not shown), and the like.The image capturing part 2 generates a plurality of captured images byrespectively capturing the object to be measured while the projectionimages are sequentially projected onto the object to be measured by theprojection part 1. The image capturing part 2 is placed in such a mannerthat the optical axis of the image capturing part 2 and the optical axisof the projection part 1 form a predetermined angle.

The control part 3 measures a geometry of the object to be measuredbased on the captured images generated by the image capturing part 2.The control part 3 can be implemented by a computer, for example.

FIGS. 1B and 1C each show an example of a captured image generated bythe image capturing part 2 while the projection part 1 projects theprojection images onto the object to be measured. As shown in FIGS. 1Band 1C, the projection part 1 projects the projection images includinglight patterns in which luminance changes depending on a position in apredetermined direction onto a target for measurement. FIG. 1B shows thecaptured image generated by the image capturing part 2 when theprojection part 1 projects, onto an even measurement surface, theprojection images including light patterns composed of light projectionregions in which light is projected and non-projection regions in whichlight is not projected. The white regions represent the light projectionregions and the black regions represent the no-projection regions. Whenthe measurement surface has no irregularities, the light patterns of thecaptured image generated by the image capturing part 2 match with thelight patterns of the projection image.

FIG. 1C shows a captured image generated by the image capturing part 2when the projection part 1 projects the light patterns onto ameasurement surface having convex portions. In the captured image ofFIG. 1C, the image of a part of the light pattern is deformed. In thecaptured image, the image of the light pattern is deformed by an amountaccording to the height of the convex portions. Therefore, the 3Dgeometry measurement apparatus 100 can measure the geometry of theobject to be measured by identifying the height of each location of theconvex portion based on the amount of deformation in the light patternimage in the captured image.

FIGS. 2A and 2B each show a projection image which the projection part 1projects onto an object to be measured. FIG. 2A shows an example of alight pattern extending in the first direction, and FIG. 2B shows anexample of a light pattern extending in the second direction. Theprojection part 1, as shown in FIG. 2A, projects the projection imageincluding the light pattern extending in the first direction (this maybe referred to as a vertical pattern below). The first direction is adirection orthogonal to the optical axis of the projection part 1 andorthogonal to the optical axis of the image capturing part 2. Theprojection part 1, as shown in FIG. 2B, may project the projection imageincluding the light pattern extending in the second direction (this maybe referred to as a horizontal pattern below). The second direction is adirection parallel to a plane including the optical axes of theprojection part 1 and the image capturing part 2.

When the above-mentioned projection image including the light pattern isprojected onto the object to be measured, the light pattern deviates inthe width direction in accordance with the 3D geometry of the object tobe measured, as shown in FIG. 1C. Also, the width of the light patternfluctuates in accordance with the 3D geometry of the object to bemeasured. In the first captured image generated by the image capturingpart 2 capturing the object to be measured while the projection imageincluding the light pattern extending in the first direction isprojected, (i) the direction corresponding to the deviation between thedirection of the optical axis of the projection part 1 and the directionof the optical axis of the image capturing part 2 and (ii) the directionof the deviation in the width direction of the light pattern match oneanother. That is, (i) a direction of an image for a line segmentgenerated by projecting a line segment connecting the starting point ofthe optical axis of the projection part 1 and a starting point of theimage capturing part 2 onto a plane where the object to be measured isplaced and (ii) the direction of the deviation in the width direction ofthe light pattern match one another. Therefore, in the first capturedimage, the sensitivity to detect the deviation of the light pattern inthe width direction and the like is high. For this reason, resolution isimproved in the measurement of the 3D geometry of the object to bemeasured.

Meanwhile, in the second captured image being generated by the imagecapturing part 2 capturing the object to be measured while theprojection image including the light pattern extending in the seconddirection, the direction corresponding to the deviation between thedirection of the optical axis of the projection part 1 and the directionof the optical axis of the image capturing part 2 and the direction ofthe deviation in the width direction of the light pattern are orthogonalto one another. That is, (i) the direction of an image for the linesegment generated by projecting the line segment connecting the startingpoint of the projection part 1 and the starting point of the imagecapturing part 2 onto the plane where the object to be measured isplaced and (ii) the direction of the deviation in the width direction ofthe light pattern are orthogonal. Therefore, the measurement resolutionof the second captured image is significantly lowered in the measurementof the 3D geometry of the object to be measured, compared to the firstcaptured image, and the 3D geometry measurement apparatus 100 cannotaccurately measure the geometry.

The 3D geometry measurement apparatus 100 identifies the 3D geometry ofthe object to be measured by analyzing the light pattern projected onthe object to be measured. However, when the surface of the object to bemeasured is glossy, there was a problem that measurement accuracy isreduced due to the multiple reflections caused by projected light fromthe projection part 1 being multiply reflected. In addition to multiplereflections, for example, there was a problem that the measuringaccuracy is lowered due to blurring of an imaging system at edges of theobject to be measured or at places where luminance change is large.Here, a position of the pixel of the projection part 1 is referred to asa projection pixel position, and a position of the pixel of the imagecapturing part 2 is referred to as a captured pixel position. As will bedescribed in detail below, the 3D geometry measurement apparatus 100determines whether or not a pixel of the captured image is a defectivepixel affected by the multiple reflections or the like, on the basis ofa positional relationship between (i) a projection light beam startingfrom the projection part 1 and passing through the pixel at theprojection pixel position and (ii) a captured light beam starting fromthe image capturing part 2 and passing through the pixel at the capturedpixel position.

FIG. 3 shows a configuration of the 3D geometry measurement apparatus100. The 3D geometry measurement apparatus 100 includes the projectionpart 1, the image capturing part 2, the control part 3, and a storageunit 4. The storage unit 4 includes a storage medium including a harddisk, a read only memory (ROM), a random access memory (RAM), and thelike. The storage unit 4 stores programs to be executed by the controlpart 3. The control part 3 is, for example, a central processing unit(CPU) and functions as a projection control part 301, a relationshipidentification part 302, a defective pixel determination part 303, ageometry identification part 304, and an abnormality detection part 305by executing the programs stored in the storage unit 4.

The projection control part 301 generates control signals for projectingthe projection images including light patterns onto the object to bemeasured and inputs the generated control signals into the projectionpart 1. The projection control part 301 controls a circuit for switchingthe projection part 1 ON/OFF for each pixel, and thus the projectioncontrol part 301 is capable of projecting a portion of the pixels of theprojection part 1 onto the object to be measured. Hereinafter, examplesof light patterns which the projection control part 301 projects will beexplained while referring to FIGS. 4A to 4F and FIGS. 5A to 5D.

[Types of Light Patterns]

FIGS. 4A to 4F respectively show examples of types of projection imageswhich the projection control part 301 projects. In FIGS. 4A to 4E theblack regions represent no-projection regions where the projection part1 does not project light, and the white regions representlight-projection regions where the projection part 1 projects light.

FIG. 4A shows a standard pattern by which light is not projected ontoany part of the object to be measured (i.e. an all-black pattern). FIG.4B shows a standard pattern by which light is projected onto the entireobject to be measured (i.e. an all-white pattern). FIGS. 4C to 4F showthe binary light patterns, which are composed of a light-projectionregion and a no-projection region and in which the stripes that have adifferent widths for each projection image are arranged in the samedirection. The light patterns shown in FIGS. 4A to 4F correspond to Graycodes and are used for identifying positions of pixels in the capturedimage. Details thereof will be described below.

FIGS. 5A to 5D respectively show examples of gradation light patternshaving sinusoidal luminance distributions and being projected onto theobject to be measured by the projection control part 301. The gradationlight patterns are light patterns in which the luminance changesdepending on a position in a predetermined direction. In the example ofthe gradation light patterns of FIGS. 5A to 5D, the luminance changes ina sinusoidal manner from the white region to the black region along thewidth direction of the stripes. Intervals between the stripes in thegradation light patterns of FIGS. 5A to 5D are constant, and spatialfrequency of the stripes in the gradation light patterns is, forexample, four times the spatial frequency of the binary light patternsof FIG. 4F.

The gradation light patterns of FIGS. 5A to 5D are different from eachother in the point that the phases of the sine waves indicating theluminance distribution differ by 90 degrees from each other, and theirluminance distributions are otherwise the same. In the presentembodiment, the projection control part 301 projects a total oftenprojection images: two standard patterns shown in FIGS. 4A and 4B, fourbinary light patterns shown in FIGS. 4C to 4F, and four gradation lightpatterns shown in FIGS. 5A to 5D. The gradation light patterns shown inFIGS. 5A to 5D, together with the light patterns shown in FIGS. 4A to4F, are used for identifying the positions of pixels in the capturedimage.

[Identifying a Pixel of the Projection Image that Corresponds to a Pixelof the Captured Image]

The relationship identification part 302 identifies the projection pixelposition which is the position of the pixel of the projection imagehaving correspondence with the captured pixel position which is theposition of the pixel of the captured image by analyzing gradationinformation of the light patterns of the captured image. If a pixelobtained by capturing a pixel A of the projection image is a pixel B ofthe captured image, the projection pixel position of the pixel A and thecaptured pixel position of the pixel B have correspondence with eachother. The method for identifying correspondence between the pixels ofthe projection image and the captured image will be described below.

As described above, the binary light patterns shown in FIGS. 4C to 4Fcorrespond to Gray codes. FIG. 6 shows examples of Gray codescorresponding to the binary light patterns shown in FIGS. 4C to 4F. Byassociating Os in the Gray codes with the no-projection regions and Iswith the light-projection regions, the binary light patterns shown inFIGS. 4C to 4F are generated.

Each position in the x-direction in FIGS. 4A to 4F and 6 is representedby a code value, which is the combination of the numbers 0 or 1 at therespective positions in the Gray codes. Position 0 in FIG. 6 correspondsto the code value of “0000,” position 1 corresponds to the code value of“0001” and position 15 corresponds to the code value of “1000.”

The image capturing part 2 captures the object to be measured while thestandard patterns shown in FIGS. 4A and 4B are respectively projectedonto the object to be measured in the projection control part 301. Therelationship identification part 302 calculates, for each pixel, anaverage value of two captured standard patterns as a median value.Similarly, regarding the captured images captured while the binary lightpatterns of FIGS. 4C to 4F are projected onto the object to be measured,the relationship identification part 302 identifies the code values ofrespective pixels by comparing the luminance values of respective pixelsin four captured images with corresponding median values. By identifyingthe code values, the relationship identification part 302 can identifywhich binary stripe is reflected at each pixel position within thebinary light pattern projected toward different positions. Therelationship identification part 302 identifies at which position fromPosition 0 to Position 15 each pixel included in the captured image isincluded.

Further, the relationship identification part 302 respectivelyidentifies the phases of the sine waves at the captured pixel positionin the captured image when the gradation light patterns havingsinusoidal luminance distributions are projected onto the object to bemeasured. The relationship identification part 302 identifies a pixelposition of the projection image that matches the phase of theidentified sine wave. Because the gradation light patterns of theprojection image have periodicity, there are a plurality of pixelpositions of the projection image that match the identified phases ofthe sine wave.

Therefore, the relationship identification part 302 identifiescorrespondence between pixel positions of the projection image and pixelpositions of the captured image on the basis of the position at whicheach pixel is included, identified on the basis of the code values ofthe Gray codes that correspond to respective pixels of the capturedimage when the binary light patterns of FIGS. 4C to 4F are projected.The relationship identification part 302 identifies correspondencebetween the pixels of the captured image and the pixels of theprojection image by selecting a correspondence included in theidentified position on the basis of the Gray codes indicated by thebinary light patterns among the plurality of correspondences identifiedby analyzing the gradation information of the gradation light patterns.Where k(=1, 2) is an index representing the first and the seconddirections, the relationship identification part 302 identifies acoordinate of a corresponding pixel (i_(p), j_(p)) of the projectionpart 1 for each pixel (i, j) of the image capturing part 2 as follows.

$\begin{matrix}{\left( {i_{p},j_{p}} \right) = \left( {\frac{p_{1}{I_{{AP},1}\left( {i,j} \right)}}{2\pi},\frac{p_{2}{I_{{AP},2}\left( {i,j} \right)}}{2\pi}} \right)} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

I_(AP,k)(i,j), where k=1, 2, is an absolute phase value of an absolutephase image of a captured image being captured while the verticalpattern and the horizontal pattern having sinusoidal luminancedistributions are projected, p_(k) is the number of pixels included inone cycle of stripes of the light pattern of the projection part 1.

In place of using the projection image including the binary lightpatterns shown in FIG. 4, the relationship identification part 302 mayuse the projection image including the gradation light patterns. Therelationship identification part 302 may be configured to identifycorrespondence between the pixel of the captured image and the pixel ofthe projection image by sequentially projecting a plurality ofprojection images having the gradation light patterns with sinusoidalluminance distributions and a stripe pattern whose cycles of stripes aredifferent from those of FIGS. 5A to 5D, in addition to the projectionimages having the gradation light patterns of FIGS. 5A to 5D.

For example, the projection part 1 may be configured to project aplurality of projection images having the first periodic gradation lightpatterns, project a plurality of projection images having the secondperiodic gradation light patterns, and project a plurality of projectionimages having the third periodic gradation light patterns. In this case,the projection part 1 can identify the geometry of the object to bemeasured by projecting the projection image having the sinusoidalluminance distributions onto the object to be measured. Further, aplurality of projection images having the first to the third periodicgradation light patterns may be projected as the gradation lightpatterns extending in the first and the second directions.

[Multiple Reflections]

The defective pixel determination part 303 determines whether or not thepixel at the captured pixel position is a defective pixel due tomultiple reflections or the like. FIGS. 7A and 7B each illustratemultiple reflections. When the object to be measured is glossy and has acomplicated shape, light emitted by the projection part 1 may enter theimage capturing part 2 after being repeatedly reflected multiple timeson the surface to be measured. In this case, as shown in FIG. 7A, thelight emitted by the projection part 1 enters one pixel of the imagingelement 22 via two or more paths.

Specifically, the light entering the imaging element 22 includes directlight, which is the light emitted by the projection part 1 and whichdirectly enters the image capturing part 2 after being diffused andreflected on the surface to be measured, and multiply reflected light,which enters the image capturing part 2 after being subjected tomultiple reflections. As a result, in the captured image captured by theimage capturing part 2, a pixel having a luminance value correspondingto black when there is no multiply reflected light may have a luminancevalue corresponding to white. In particular, multiple reflection islikely to occur when the object to be measured contains metal or thelike which is likely to cause random reflection.

FIG. 7B shows an example of a captured image affected by multiplereflections. FIG. 7B corresponds to FIG. 1C, but due to the influence ofmultiply reflected light, the shaded portions have luminance which isdifferent from the luminance in FIG. 1C. Also, due to the influence ofmultiply reflected light, distortion or the like may occur in thesinusoidal waveform shown in the luminance distributions of thegradation light patterns.

[Determining Defective Pixels]

The defective pixel determination part 303 determines whether or not thepixel at the captured pixel position is a defective pixel on the basisof the positional relationship between (i) the projection light beamstarting from the projection part 1 and passing through the pixel at theprojection pixel position and (ii) the captured light beam starting fromthe image capturing part 2 and passing through the pixel at the capturedpixel position having correspondence with the captured pixel position.FIGS. 8 and 9 are diagrams for explaining the principle of thedetermination of defective pixels.

FIG. 8 shows a light path of direct reflection light. Light emitted froman optical center O1 of the projection part 1 passes through aprojection pixel position A1 on an image plane of the projection part 1,and diffuses and reflects at one position MP on the object to bemeasured. The light reflected at the position MP passes through acaptured pixel position B1 in an image plane of the image capturing part2.

FIG. 9 shows a light path of multiply reflected light. It is assumedthat a light passing through a projection pixel position A2 that isdifferent from the projection pixel position A1 on the image plane ofthe projection part 1 becomes multiply reflected light which isreflected at a plurality of positions on the object to be measured. Thismultiply reflected light is indicated by the thick broken lines. Themultiply reflected light passes through the captured pixel position B1in the image plane of the image capturing part 2.

As shown in FIG. 8, in the case of the direct reflected light reflectedonly once from the object to be measured, the projection light beampassing through the pixel of the projection pixel position A1 and thecaptured light beam passing through the captured pixel position B1intersect at one measurement point MP on the object to be measured. Thelight passing through the pixel at the projection pixel position A2reaches the captured pixel position B1 due to the occurrence of multiplereflections reflecting from the plurality of positions on the object tobe measured, but when multiple reflections do not occur, the lightpassing through the projection pixel position A2 does not reach thecaptured pixel position B1. That is, if multiple reflections do notoccur, the projection light beam passing through the projection pixelposition A2 does not intersect with the captured light beam passingthrough the captured pixel position B1. By using this characteristic,the defective pixel determination part 303 determines whether a pixel isa defective pixel or not.

FIG. 10 illustrates a method of determining the defective pixel by thedefective pixel determination part 303. The defective pixeldetermination part 303 identifies a positional relationship between theprojection light beam and the captured light beam as follows.

[Calculating 3D Position on Captured Light Beam]

The defective pixel determination part 303 identifies a captured lightbeam L_(B1) starting from the image capturing part 2 and passing througha captured pixel position B1(i, j). Since the orientation of the imagecapturing part 2 is constant, the captured light beam L_(B1) startingfrom the optical center (O1 in FIG. 10) of the projection part 1 andpassing through the captured pixel position B1(i, j) is uniquelydetermined by the arrangement of the lens 21. Information foridentifying the captured light beam L_(B1) is stored in the storage unit4 in advance, and the defective pixel determination part 303 reads theinformation for identifying the captured light beam L_(B1) from thestorage unit 4. The information for identifying the captured light beamL_(B1) is, for example, information showing directions of straight lineswith the optical center of the projection part 1 as the origin orcoordinates of points on the straight lines.

The defective pixel determination part 303 identifies a projection lightbeam plane in a predetermined direction passing through a projectionpixel position A2(i _(p), j_(p)) being identified to have correspondencewith the captured pixel position B1 by the relationship identificationpart 302. Specifically, the defective pixel determination part 303identifies a projection light beam plane corresponding to a horizontalcoordinate value i_(p) of the projection pixel position A2(i _(p),j_(p)). The projection pixel position having the horizontal coordinatevalue i_(p) exists on a straight line EF in the image plane of theprojection part 1 shown in FIG. 10. Assuming that a straight lineobtained by projecting the straight line EF to the object to be measuredside from the optical center O1 of the projection part 1 as a startingpoint is a straight line E′F′, a measurement point MP on the object tobe measured corresponding to the projection pixel position having thehorizontal coordinate value i_(p) exists in a projection light beamplane including three points O1, E′, and F′. The defective pixeldetermination part 303 identifies, as the first 3D position B1′, aposition where the projected light beam plane including the three pointsO1, E′, and F′ and a captured light beam L_(B1) intersect. When multiplereflections or the like do not occur, the obtained intersection pointB1′ approximately matches with the measurement point MP on the object tobe measured corresponding to the captured pixel position B1(i,j).

[Calculating 3D Position on Projection Light Beam]

The defective pixel determination part 303 identifies a projection lightbeam L_(A2) starting from the optical center O1 of the projection part 1and passing through the projection pixel position A2(i _(p), j_(p)) ofthe projection part 1. Since the orientation of the projection part 1 isconstant, the projection light beam L_(A2) starting from the opticalcenter O1 of the projection part 1 and passing through the projectionpixel position A2(i _(p), j_(p)) of the projection part 1 is uniquelydetermined. Information for identifying the projection light beam L_(A2)is stored in the storage unit 4 in advance, and the defective pixeldetermination part 303 reads the information for identifying theprojection light beam L_(A2) from the storage unit 4. The informationfor identifying the projection light beam L_(A2) is, for example,information indicating directions of straight lines with the opticalcenter O1′ of the image capturing part 2 as the origin or coordinates ofpoints on the straight lines.

Also, the defective pixel determination part 303 identifies a capturedlight beam plane passing through the captured pixel position B1(i, j) ina direction specified in advance. More specifically, the defective pixeldetermination part 303 identifies the captured light beam planecorresponding to the horizontal coordinate value i of the captured pixelposition B1(i, j). The captured pixel position having the horizontalcoordinate value i is on a straight line GH in the image plane of theimage capturing part 2 shown in FIG. 10. The point at which the capturedlight beams passing through the plurality of captured pixel positions inthe image plane of the image capturing part 2 intersect is denoted byO1′. Assuming that a straight line obtained by projecting the straightline GH to the object to be measured side from O1′ as a starting pointis a straight line G′H′, the measurement point MP on the object to bemeasured corresponding to the captured pixel position having thehorizontal coordinate value i exists in a captured light beam planeincluding three points O1′, G′, and H′. The defective pixeldetermination part 303 identifies, as the second 3D position A2′, aposition where the captured light beam plane including the three pointsO1′, G′, and H′ and the projection light beam L_(A2) intersect. Whenmultiple reflections or the like do not occur, the obtained intersectionpoint A2′ approximately matches the measurement point MP on the objectto be measured corresponding to the captured pixel position B1(i, j).

[Comparing Two 3D Positions]

The defective pixel determination part 303 compares the first 3Dposition B1′ on the captured light beam with the second 3D position A2′on the projection light beam to determine whether or not the pixel inthe captured image is a defective pixel. When the first 3D position B1′and the second 3D position A2′ are not affected by multiple reflectionsor the like, they approximately match with each other. On the otherhand, in the case of being affected by multiple reflections or the like,the difference between the first 3D position B1′ and the second 3Dposition A2′ becomes large.

When a distance D between the first 3D position B1′ and the second 3Dposition A2′ shown in FIG. 10 exceeds a threshold value, the defectivepixel determination part 303 determines that the pixel at the capturedpixel position B1 is a defective pixel. On the other hand, when thedistance D between the first 3D position B1′ and the second 3D positionA2′ is equal to or less than the threshold value, the defective pixeldetermination part 303 determines that the pixel on the captured pixelposition B1 is not a defective pixel. The threshold value is, forexample, a statistical quantity of an error which occurs between thefirst 3D position B1′ and the second 3D position A2′ when the pixel atthe captured pixel position B1 is not affected by multiple reflectionsor the like.

The geometry identification part 304 can identify the 3D positioncorresponding to the captured pixel position by using three coordinatevalues among four coordinate values included in one captured pixelposition (i, j) and the projection pixel position (i_(p), j_(p))identified by the relationship identification part 302 as havingcorrespondence with the captured pixel position. The above procedure isequivalent to comparing the 3D position obtained from the combination ofthe coordinate value i, the coordinate value j, and the coordinate valuei_(p) with the 3D position obtained from the combination of thecoordinate value i, the coordinate value i_(p), and the coordinate valuej_(p).

[Distance Between Captured Light Beam and Projection Light Beam]

The defective pixel determination part 303 may determine whether or notthe pixel at the captured pixel position is a defective pixel on thebasis of a distance between the captured light beam and the projectionlight beam. FIG. 11 illustrates another method of determining thedefective pixel by the defective pixel determination part 303. Thedefective pixel determination part 303 identifies a captured light beamL_(B1) passing through the captured pixel position B1(i, j) of the imagecapturing part 2 and a projection light beam L_(A2) passing through aprojection pixel position A2(i _(p), j_(B1)) that the relationshipidentification part 302 identified to have correspondence with thecaptured pixel position B1. The defective pixel determination part 303calculates the shortest distance D′ between the captured light beam andthe projection light beam.

When the obtained shortest distance D′ exceeds a reference value, thedefective pixel determination part 303 determines that the pixel at thecaptured pixel position B1 is the defective pixel. On the other hand,when the obtained shortest distance D′ is equal to or less than thereference value, the defective pixel determination part 303 determinesthat the captured pixel position B1 is not a defective pixel. Thereference value is, for example, based on a statistical quantity of theshortest distance D′ when the pixel at the captured pixel position B1 isnot affected by multiple reflections or the like.

[Using Normal Line]

FIG. 12 illustrates still another method of determining the defectivepixel by the defective pixel determination part 303. The defective pixeldetermination part 303 may calculate the normal line of the measurementsurface of the object to be measured on the basis of surroundinginformation of the captured pixel position of interest, and determinethe defective pixel on the basis of the calculated normal line. Thedefective pixel determination part 303 selects three or more capturedpixel positions B1 to B3 within a predetermined range from the capturedpixel position of interest. The predetermined range is, for example, arange including several to several tens of captured pixel positions inthe vicinity of the captured pixel position of interest. By the methoddescribed above, the defective pixel determination part 303 identifiesthe first 3D positions B1′ to B3′ corresponding to the selected capturedpixel positions B1 to B3, respectively.

The defective pixel determination part 303 identifies a first planedetermined by the identified first 3D positions B1′ to B3′. When thethree captured pixel positions B1 to B3 are selected, the defectivepixel determination part 303 identifies the first plane including all ofthe first 3D positions B1′ to B3′. When four or more captured pixelpositions within the predetermined range from the captured pixelposition of interest are selected, the defective pixel determinationpart 303 identifies four or more first 3D positions corresponding to theselected captured pixel positions. For example, the defective pixeldetermination part 303 identifies the first plane such that the sum ofsquares of distances from the identified four or more first 3D positionsto the first plane is minimized.

In the same manner, the defective pixel determination part 303identifies the second 3D positions corresponding to three or morecaptured pixel positions, respectively. The defective pixeldetermination part 303 identifies the second plane determined by theidentified second 3D positions. The first 3D positions B1′ to B3′ are onan extension line obtained by extending the captured light beams fromthe image capturing part 2 passing through the selected captured pixelpositions B1 to B3 toward the object to be measured, and the first planeis determined by these first 3D positions B1′ to B3′. On the other hand,the second 3D positions are on extension lines obtained by extending theprojection light beams from the projection part 1 passing through theprojection pixel positions having correspondence with the selectedcaptured pixel positions B1 to B3 toward the object to be measured, andthe second plane is determined by these second 3D positions.

The defective pixel determination part 303 determines whether or not thecaptured pixel position is a defective pixel on the basis ofcorrespondence between the first plane and the second plane. Morespecifically, the defective pixel determination part 303 compares thefirst normal line passing through the first plane with the second normalline passing through the second plane. For example, the defective pixeldetermination part 303 calculates at least one of a difference ofinclination and a distance between the first normal line N passingthrough the center of gravity of the triangle composed of the first 3Dpositions B1′ to B3′ and the second normal line (not shown) passingthrough the center of gravity of the triangle composed of the second 3Dpositions.

When the difference between the inclination of the first normal line andthe inclination of the second normal line is equal to or less than apredetermined angle, or the shortest distance between the first normalline and the second normal line is equal to or less than a predetermineddistance, the defective pixel determination part 303 determines that thepixel at the captured pixel position of interest is not a defectivepixel. On the other hand, when the difference of inclination between thefirst normal line and the second normal line exceeds a predeterminedangle, or when the shortest distance between the first normal line andthe second normal line exceeds the predetermined distance, the defectivepixel determination part 303 determines that the pixel at the capturedpixel position of interest is a defective pixel.

The predetermined angle and the predetermined distance are determined bypersons skilled in the art according to the measurement accuracyrequired in the 3D geometry measurement. With such configurations, thedefective pixel determination part 303 determines whether or not thepixel at the captured pixel position is a defective pixel inconsideration of the surrounding pixels, and therefore the accuracy ofdetermining defective pixels can be improved.

[Identify 3D Geometry]

The geometry identification part 304 identifies the 3D geometry of theobject to be measured on the basis of pixel values of the captured pixelpositions excluding the position of the pixel determined to be thedefective pixel by the defective pixel determination part 303. Thegeometry identification part 304 obtains the respective first 3Dpositions identified by the defective pixel determination part 303 forthe plurality of captured pixel positions of the captured image. Thegeometry identification part 304 identifies the 3D geometry of theobject to be measured as an aggregate of the obtained 3D positions. Atthis time, the geometry identification part 304 does not include thefirst 3D positions corresponding to the captured pixel positionsdetermined to be defective pixels by the defective pixel determinationpart 303 in the 3D geometry of the object to be measured.

[Averaging First 3D Position and Second 3D Position]

The geometry identification part 304 may identify the 3D geometry of theobject to be measured by obtaining the respective 3D positionsidentified by the defective pixel determination part 303 for theplurality of captured pixel positions of the captured image. Thegeometry identification part 304 may identify the 3D geometry of theobject to be measured on the basis of the mean value of the 3Dcoordinates of the first 3D positions and the mean value of the second3D positions.

If a distance between the first 3D position and the second 3D positionbecomes large for the plurality of captured pixel positions, there is apossibility that, not the influence of the multiply reflected light orthe like, but defects have occurred in a state of the projection part 1or the image capturing part 2. For example, there is a possibility thata deviation in a positional relationship between the projection part 1and the image capturing part 2 has occurred. Therefore, the abnormalitydetection part 305 may detect that the state of the projection part 1 orthe image capturing part 2 of the 3D geometry measurement apparatus 100is not appropriate, using the following method.

First, the abnormality detection part 305 obtains the distance betweenthe first 3D position and the second 3D position corresponding to thecaptured pixel position from the defective pixel determination part 303.The abnormality detection part 305 obtains respective distances betweenthe first 3D position and the second 3D position for the plurality ofcaptured pixel positions, and calculates a statistical quantity such asa mean value of the obtained distances.

The abnormality detection part 305 detects an abnormality of the 3Dgeometry measurement apparatus 100 on the basis of the obtainedstatistical quantity. More specifically, the abnormality detection part305 self-diagnoses that the alignment state of the projection part 1 andthe image capturing part 2 of the 3D geometry measurement apparatus 100is not appropriate when the obtained statistical quantity exceeds anallowable value. In this case, the abnormality detection part 305displays on a display unit (not shown) a message indicating that acalibration of the alignment state of the projection part 1 and theimage capturing part 2 needs to be made. Taking the desired accuracy ofmeasurement into account, the allowable value is specified by a personskilled in the art, as appropriate.

On the other hand, when the obtained statistical quantity is equal to orless than the allowable value, the abnormality detection part 305self-diagnoses that the alignment states of the projection part 1 andthe image capturing part 2 of the 3D geometry measurement apparatus 100are appropriate. With such configurations, the abnormality detectionpart 305 can self-diagnose whether or not the positional relationbetween the projection part 1 and the image capturing part 2 isdeviated, and so the reliability of the 3D geometry measurementapparatus 100 can be improved.

[Defective Pixel Determination Process]

FIG. 13 is a flowchart for illustrating a procedure of a defective pixeldetermination process performed by the defective pixel determinationpart 303. This procedure starts, for example, when a user givesinstructions to measure the 3D geometry of the object to be measured byusing an operation key (not shown) of the 3D geometry measurementapparatus 100.

First, the projection control part 301 controls the projection part 1 toproject the projection image onto the object to be measured (S101).Next, the image capturing part 2 captures the object to be measuredwhile the projection image is projected onto the object to be measured(S102). The relationship identification part 302 identifies a projectionpixel position that has correspondence with the captured pixel position(S103).

The defective pixel determination part 303 identifies a captured lightbeam L_(BK) passing through a captured pixel position B_(k)(i_(k),j_(k)), where k=1, 2, . . . , of the image capturing part 2, andidentifies a projection light beam plane corresponding to a coordinatevalue i_(pK) which is one of the coordinate values of the projectionpixel position A_(k)(i_(pk), j_(pk)) identified by the relationshipidentification part 302 as a position having correspondence with thecaptured pixel position B_(k). The defective pixel determination part303 identifies, as the first 3D position a_(k), a position at which theidentified projection light beam plane and the captured light beamL_(Bk) intersect (S104).

The defective pixel determination part 303 identifies a projection lightbeam L_(Ak) passing through the same projection pixel positionA_(k)(i_(pk), j_(pk)), and identifies a captured light beam planecorresponding to a coordinate value i_(k) which is one of the coordinatevalues of the captured pixel position B_(k)(i_(k), j_(k)). The defectivepixel determination part 303 identifies, as the second 3D positionb_(k), a position at which the identified captured light beam plane andthe projection light beam L_(Ak) intersect (S105).

The defective pixel determination part 303 determines whether a distancebetween (i) the first 3D position a_(k) on the captured light beamL_(Bk) and (ii) the second 3D position b_(k) on the projection lightbeam L_(Ak) exceeds the threshold value (S106). When the distancebetween the first 3D position a_(k) and the second 3D position b_(k)exceeds the threshold value (YES in S106), the defective pixeldetermination part 303 determines that the pixel at the captured pixelposition B_(k) is a defective pixel (S107). The defective pixeldetermination part 303 determines whether or not there remains any pixelof the captured pixel position B_(k) for which the determination ofwhether the pixel is defective has not been made (S108). When thedefective pixel determination part 303 has determined for all of thepixels of the captured pixel position B_(k) whether they are defectivepixels or not (NO in S108), the geometry identification part 304determines the 3D geometry of the object to be measured on the basis ofthe pixel values of the captured pixel position B_(k) excluding thepositions of the pixels determined to be defective pixels by thedefective pixel determination part 303 (S109), and finishes theprocessing.

When the distance between the first 3D position a_(k) on the capturedlight beam L_(Bk) and the second 3D position b_(k) on the projectionlight beam L_(Ak) in the determination of step S106 is equal to or lessthan the threshold value (NO in S106), the defective pixel determinationpart 303 determines that the pixel at the captured pixel position B_(k)is not a defective pixel (S110), and proceeds to the determination ofstep S108. If it is determined in the determination of step S108 thatthere remains a pixel at the captured pixel position B_(k) for which thedetermination of whether the pixel is defective has not been made (Yesin S108), the defective pixel determination part 303 returns toprocessing of step S104 for another captured pixel position B_(k).

According to the present embodiment, the defective pixel determinationpart 303 determines whether or not the pixel at the captured pixelposition is a defective pixel on the basis of the positionalrelationship between (i) the projection light beam starting from theprojection part 1 and passing through the pixel at the projection pixelposition and (ii) the captured light beam starting from the imagecapturing part 2 and passing through the pixel at the captured pixelposition having correspondence with the projection pixel position. Withsuch configurations, the defective pixel determination part 303 canprevent the reduction of measurement accuracy occurring when therelationship identification part 302 erroneously identifies theprojection pixel position having correspondence with the captured pixelposition due to multiple reflections. Also, the defective pixeldetermination part 303 can prevent the reduction of measurement accuracymeasuring 3D geometry occurring when the relationship identificationpart 302 erroneously identifies the correspondence due to, besides themultiple reflections, blurring of the image capturing part 2 at edges ofthe object to be measured or at places where the luminance change islarge. As described above, the defective pixel determination part 303can prevent measurement errors caused by various measurement defects.

[Re-Measurement Process]

Since defective pixels are often caused by multiply reflected light, itis possible to prevent the influence of multiply reflected light byprojecting a projection image excluding projection pixels at positionsdetected as defective pixels. Therefore, when the defective pixeldetermination part 303 determines that the pixel at the captured pixelposition is a defective pixel, the projection control part 301 mayproject a projection image (hereinafter, the first selected projectionimage) from which all of the pixels at the projection pixel positionshaving correspondence with the captured pixel positions determined to bedefective pixels by the defective pixel determination part 303 areexcluded from among the plurality of pixels included in the projectionimage onto the object to be measured again.

The relationship identification part 302 identifies a captured pixelposition having correspondence with the projection pixel position of thefirst selected projection image. Since the defective pixels may beinfluenced by multiply reflected light, the projection control part 301prevents the influence of the multiply reflected light by projecting thefirst selected projection image that does not include defective pixels.Therefore, the relationship identification part 302 can identify thecorrespondence between the projection pixel position and the capturedpixel position more accurately.

It can be considered that the defective pixel due to multiplereflections occurs by simultaneously projecting the projection imagesincluding a number of pixels onto the object to be measured. Therefore,when the defective pixel determination part 303 determines that thepixel at the captured pixel position is a defective pixel, theprojection control part 301 may project a projection image (hereinafterreferred to as the second selected projection image) including only thepixels at the projection pixel positions having correspondence with thecaptured pixel positions determined to be defective pixels by thedefective pixel determination part 303 from among the plurality ofpixels included in the projection image onto the object to be measuredagain, and perform the measurement again in order to reduce the numberof pixels to be simultaneously projected.

The relationship identification part 302 identifies a captured pixelposition having correspondence with a projection pixel position of thesecond selected projection image. The projection control part 301decreases the number of pixels that are simultaneously projected,compared to the case when all projection images are projected, byprojecting the second selected projection image. The relationshipidentification part 302 can increase the number of pixels that are usedfor identifying the 3D geometry of the object to be measured byestimating the projection pixel position having correspondence with thecaptured pixel position of the pixel detected as a defective pixel bythe defective pixel determination part 303 again.

[Variations]

In the above embodiment, the projection control part 301 projectsprojection patterns for a space coding method and a phase shift methodas projection patterns in the first direction and the second direction.That is, the projection control part 301 projects, as light patternsexhibiting sinusoidal luminance distributions, the projection imagehaving light patterns extending in the first direction and theprojection image having light patterns extending in the second directiononto the object to be measured. Also, the projection control part 301projects, as binary light patterns, the projection image having lightpatterns extending in the first direction and the projection imagehaving light patterns extending in the second direction onto the objectto be measured.

The present invention, however, is not limited to this. The lightpatterns in the first direction and the light patterns in the seconddirection do not need to be the same. For example, the projectioncontrol part 301 may project only the projection patterns for the phaseshift method with respect to the projection patterns in the seconddirection. In this case, the projection control part 301 projects theprojection image having light patterns exhibiting sinusoidal luminancedistributions as light patterns extending in the second direction ontothe object to be measured, and does not project the projection imagehaving binary light patterns onto the object to be measured.

When the projection control part 301 projects the projection patterns inthe second direction, the relationship identification part 302 obtains aphase value I_(RP,2)(i, j). In this case, the absolute phase valueI_(AP,2) of the projection patterns in the second direction can beexpressed by the following equation using a certain unknown integer mand a phase value I_(AP,2)(i, j), and a plurality of candidates can beconsidered.

[Equation 2]

I _(AP,2)=2πm+I _(RP,2)(i,j)  (a)

There are a plurality of candidates for projection pixel positionshaving correspondence with the captured pixel positions, as shown in theequations below, where i_(p) and j_(p)(m) respectively show the i_(p)-thpixel from the left edge in the second direction and the j_(p)(m)-thpixel from the top edge in the first direction.

$\begin{matrix}\left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack & \; \\{\left( {i_{p},{j_{p}(m)}} \right) = \left( {\frac{p_{1}{I_{{AP},1}\left( {i,j} \right)}}{2\pi},\frac{p_{2}{I_{{AP},2}\left( {i,j,m} \right)}}{2\pi}} \right)} & (b)\end{matrix}$

Here, since there are the plurality of candidates for the projectionpixel position, the defective pixel determination part 303 identifies aplurality of second 3D positions. On the other hand, since thecoordinate values i_(p) in the first direction of the projection pixelposition are the same in the plurality of candidates, the defectivepixel determination part 303 identifies one first 3D position. Thedefective pixel determination part 303 calculates a value of mindicating the second 3D position closest to the first 3D positioncorresponding to the same captured pixel position among the second 3Dpositions obtained for the plurality of candidates.

The defective pixel determination part 303 can determine whether or notthe pixel at the captured pixel position is a defective pixel bydetermining whether or not a distance between the first 3D position andthe second 3D position closest to the first 3D position exceeds athreshold value. With such configurations, the projection control part301 can further reduce the number of light patterns to be projected ontothe object to be measured. Therefore, the projection control part 301can shorten the measurement time.

When projecting the light patterns in the second direction, thedefective pixel determination part 303 can narrow down the plurality ofcandidates for the projection pixel position having correspondence withthe captured pixel position in order to reduce the calculation amount.The defective pixel determination part 303 identifies the second 3Dposition for each of the plurality of candidates. By defining in advancea range of measurable 3D positions as a range which the second 3Dposition can assume, a range of m that can correspond to the pluralityof candidates is limited, and thus the candidates can be narrowed down.

For example, when planes that sufficiently cover a range of measurable3D space are placed on the nearest side and on the farthest side of the3D geometry measurement apparatus 100, by measuring in advance pixelvalues of the respective planes onto which lateral light patterns areprojected, the range of m that can correspond to the plurality ofcandidates can be calculated. It should be noted that since the pixelvalues of the lateral light patterns do not greatly change due todifference in the geometry of the object to be measured, there is anadvantage that the range of m defined for the pixels at the respectivecaptured pixel positions of the image capturing part 2 becomesrelatively small.

The defective pixel determination part 303 can perform the sameprocessing for light patterns other than the light patterns in thesecond direction, for example, light patterns in the first direction. Inparticular, in the case of the light patterns in the second direction,the defective pixel determination part 303 can greatly narrow down thecandidates by defining the range of m using the above-described method,and therefore processing can be simplified.

In the above explanation, the projection control part 301 projects theprojection image including the light patterns extending in the firstdirection and the projection image including the light patternsextending in the second direction onto the object to be measured. Thepresent invention, however, is not limited to the example of projectingthe light patterns extending in the first direction and the seconddirection, and the projection control part 301 may project a projectionimage including light patterns obtained by combining light patternsextending in arbitrary directions.

Also, the projection control part 301 may be configured to repeat theprocessing of projecting projection images including light patternsextending in another direction onto the object to be measured. Forexample, the projection control part 301 sequentially projectsprojection images including light patterns extending in the firstdirection to the N direction (N is the natural number). The projectioncontrol part 301 may be configured to stop projecting the projectionimages including the light patterns based on a range of defective pixelsnewly detected from the captured image obtained by projecting theprojection image including the light patterns extending in the N-thdirection. That is, the projection control part 301 may be configured tostop projecting the projection images including the light patterns whena range of defective pixels not detected from the captured image inwhich the light patterns extending in the first direction to the(N−1)-th direction are projected, among the defective pixels detectedfrom the captured image in which the projection image including thelight patterns extending in the N-th direction are projected, is equalto or less than a threshold value. The threshold value is, for example,a value indicating that the influence of multiply reflected light hasbecome sufficiently small.

The projection control part 301 may sequentially project a plurality ofprojection images including light patterns those cycles of stripes aredifferent from each other. For example, the projection control part 301may project the projection image including the light patterns extendingin the first direction onto the object to be measured, and then mayadditionally project the projection image including light patternsextending in the first direction and having different cycles onto theobject to be measured. Also, the projection control part 301 may projectthe projection image including light patterns extending in the seconddirection onto the object to be measured, and then may additionallyproject the projection image including light patterns extending in thesecond direction and having different cycles onto the object to bemeasured. When the projection image including light patterns with thedifferent cycles is projected, the phase of the multiply reflected lightoverlapping the direct light changes. For this reason, the defectivepixel determination part 303 can detect the pixels affected by themultiply reflected light more accurately.

Also, in the above description, the example of the case where theprojection control part 301 projects each projection image usingprojection light with the same wavelength was explained. However, thepresent invention is not limited to this case. For example, theprojection control part 301 may project a plurality of projection imagesincluding light patterns extending in the first direction onto theobject to be measured using light of a first wavelength, and project aprojection image including light patterns extending in the seconddirection onto the object to be measured using light of a secondwavelength. By adopting this configuration, the projection imageincluding the light patterns extending in the first direction and theprojection image including the light patterns extending in the seconddirection can be projected onto the object to be measured at the sametime, and the amount of measurement time can be reduced. The thresholdvalue may be changed with respect to each wavelength.

Also, in the above description, the example of the case where theprojection control part 301 projects the projection image including thestripe patterns as the light patterns was explained. However, thepresent invention is not limited to this, and for example, theprojection control part 301 may project a projection image includingcheckered patterns as light patterns. The projection control part 301can project a projection image including any light patterns onto theobject to be measured, provided that the relationship identificationpart 302 can identify a projection pixel position having correspondencewith the captured pixel position by a single light pattern or aplurality of light patterns.

The defective pixel determination part 303 may output a determinationresult as to whether or not the pixel is a defective pixel. For example,the defective pixel determination part 303 displays the determinationresult on a display or transmits the determination result to an externalPC. When the defective pixel determination part 303 outputs thedetermination result, the user who measures the geometry of the objectto be measured can check the determination result, and if the userdetermines that the measurement accuracy does not reach a desiredaccuracy, the measurement accuracy can be improved by re-measurement orchanging the placement position of the object to be measured.

Although the present invention has been described using the embodimentsdescribed above, the technical scope of the present invention is notlimited to the ranges described in the above embodiments, and variousmodifications and changes can be made within the scope of the gistthereof. For example, the specific embodiment of the distribution andintegration of devices is not limited to the above-described embodiment,and all or part of the embodiment can be configured to be functionallyor physically distributed and integrated in arbitrary units. Alsoincluded in the embodiments of the present invention are new embodimentsresulting from any combination of multiple embodiments. The effect ofthe new embodiment caused by the combination is the same as the effectof the original embodiment.

What is claimed is:
 1. A three-dimensional geometry measurementapparatus that measures a three-dimensional geometry of an object to bemeasured by projecting, onto the object to be measured, a projectionimage including a light pattern in which luminance changes depending ona position, the three-dimensional geometry measurement apparatuscomprising: a projection part that projects the projection image ontothe object to be measured; an image capturing part that generates acaptured image by capturing the object to be measured on which theprojection image is projected; a relationship identification part thatidentifies a projection pixel position which is a position of a pixel ofthe projection image having correspondence with a captured pixelposition which is a position of a pixel of the captured image; and adefective pixel determination part that determines whether or not thepixel at the captured pixel position is a defective pixel on the basisof a positional relationship between (i) a projection light beamstarting from the projection part and passing through the pixel at theprojection pixel position and (ii) a captured light beam starting fromthe image capturing part and passing through the pixel at the capturedpixel position having correspondence with the projection pixel position.2. The three-dimensional geometry measurement apparatus according toclaim 1, further comprising a geometry identification part thatidentifies the three-dimensional geometry of the object to be measuredon the basis of pixel values of the captured pixel positions excludingthe position of the pixel determined to be the defective pixel by thedefective pixel determination part.
 3. The three-dimensional geometrymeasurement apparatus according to claim 1, wherein the defective pixeldetermination part determines whether or not the pixel at the capturedpixel position is a defective pixel on the basis of a distance betweenthe captured light beam and the projection light beam.
 4. Thethree-dimensional geometry measurement apparatus according to claim 2,wherein the defective pixel determination part (i) identifies, as afirst three-dimensional position, a position at which the captured lightbeam passing through the captured pixel position intersects with aprojection light beam plane in a predetermined direction passing throughthe projection pixel position having correspondence with the capturedpixel position, (ii) specifies, as a second three-dimensional position,a position at which the projection light beam passing through theprojection pixel position intersects with the captured light beam planein a predetermined direction passing through the captured pixelposition, and (iii) determines that the pixel at the captured pixelposition is a defective pixel when a distance between the firstthree-dimensional position and the second three-dimensional position isgreater than a threshold value.
 5. The three-dimensional geometrymeasurement apparatus according to claim 4, wherein the defective pixeldetermination part determines whether or not the captured pixel positionis a defective pixel on the basis of correspondence between (i) a firstplane determined by three or more of the first three-dimensionalpositions corresponding to three or more of the captured pixel positionswithin a predetermined range from the captured pixel position and (ii) asecond plane determined by three or more of the second three-dimensionalpositions corresponding to three or more of the captured pixelpositions.
 6. The three-dimensional geometry measurement apparatusaccording to claim 4, wherein the geometry identification partidentifies the three-dimensional geometry of the object to be measuredon the basis of the mean value of three-dimensional coordinates of thefirst three-dimensional positions and the mean value of the secondthree-dimensional positions.
 7. The three-dimensional geometrymeasurement apparatus according to claim 4, further comprising anabnormality detection part that obtains distances between the firstthree-dimensional positions and the second three-dimensional positionsto detect an abnormality of the three-dimensional geometry measurementapparatus on the basis of a statistical quantity of distances obtainedfor a plurality of captured pixel positions.
 8. The three-dimensionalgeometry measurement apparatus according to claim 1, wherein theprojection part projects a projection image, from which all of thepixels at the projection pixel positions having the correspondence withthe captured pixel positions determined to be defective pixels by thedefective pixel determination part are excluded from among the pluralityof pixels included in the projection image, onto the object to bemeasured again when the defective pixel determination part determinesthat a pixel at a captured pixel position is a defective pixel.
 9. Thethree-dimensional geometry measurement apparatus according to claim 1,wherein the projection part projects a projection image, including onlythe pixels at the projection pixel positions having correspondence withthe captured pixel positions determined to be defective pixels by thedefective pixel determination part from among the plurality of pixelsincluded in the projection image, onto the object to be measured againwhen the defective pixel determination part determines that a pixel at acaptured pixel position is a defective pixel.
 10. The three-dimensionalgeometry measurement apparatus according to claim 1, wherein theprojection part projects a projection image including the light patternextending in a first direction orthogonal to a plane including anoptical axis of the image capturing part and an optical axis of theprojection part, and a projection image including the light patternextending in a second direction parallel to the plane including theoptical axis of the image capturing part and the optical axis of theprojection part.
 11. The three-dimensional geometry measurementapparatus according to claim 1, wherein the projection part projects aprojection image including the light pattern of a binary image and aprojection image including the light pattern having a sinusoidalluminance distribution onto the object to be measured.
 12. Thethree-dimensional geometry measurement apparatus according to claim 1,wherein the projection part sequentially projects a plurality ofprojection images including the light patterns whose cycles of stripesare different from each other.
 13. A three-dimensional geometrymeasurement method that measures a three-dimensional geometry of anobject to be measured by projecting, onto the object to be measured, aprojection image including a light pattern in which luminance changesdepending on a position, the method comprising: projecting theprojection image onto the object to be measured by a projection part;generating, by an image capturing part, a captured image by capturingthe object to be measured on which the projection image is projected;identifying a projection pixel position which is a position of a pixelof the projection image having correspondence with a captured pixelposition which is a position of a pixel of the captured image; anddetermining whether or not the pixel at the captured pixel position is adefective pixel on the basis of a positional relationship between (i) aprojection light beam starting from the projection part and passingthrough the pixel at the projection pixel position and (ii) a capturedlight beam starting from the image capturing part and passing throughthe pixel at the captured pixel position having correspondence with theprojection pixel position.